Distribution of antibiotic resistance genes and their association with bacteria and viruses in decentralized sewage treatment facilities

The distribution of antibiotic resistance genes(ARGs)has been intensively studied in large-scale wastewater treatment plants and livestock sources.However,small-scale decentralized sewage treatment facilities must also be explored due to their possible direct exposure to residents.In this study,six wastewater treatment facilities in developed rural areas in eastern China were investigated to understand their risks of spreading ARGs.Using metagenomics and network analysis tools,ARGs and bacterial and viral communities were identified in the influent(INF)and effluent(EFF)samples.The dominant ARGs belonged to the bacitracin class,which are different from most of municipal wastewater treatment plants(WWTPs).The dominant hosts of ARGs are Acidovorax in bacterial communities and Prymnesiovirus in viral communities.Furthermore,a positive relationship was found between ARGs and phages.The ARGs significantly correlated with phages were all hosted by specific genera of bacteria,indicating that phages had contributed to the ARG’s proliferation in sewage treatment facilities.Paying significant concern on the possible enhanced risks caused by bacteria,viruses and their related ARGs in decentralized sewage treatment facilities is necessary.

Genome-resolved metagenomic analysis reveals different functional potentials of multiple Candidatus Brocadia species in a full-scale swine wastewater treatment system

The increasing application of anammox processes suggests their enormous potential for nitrogen removal in wastewater treatment facilities.However,the functional potentials and ecological differentiation of cooccurring anammox species in complex ecosystems have not been well elucidated.Herein,by utilizing functional reconstruction and comparative genome analysis,we deciphered the cooccurring mechanisms of four Candidatus Brocadia species that were spontaneously enriched in a full-scale swine wastewater treatment system.Phylogenetic analysis indicated that species SW172 and SW745 were closely related to Ca.Brocadia caroliniensis and Ca.Brocadia sapporoensis,respectively,whereas the dominant species SW510 and SW773,with a total average abundance of 34.1%,were classified as novel species of the genus Ca.Brocadia.Functional reconstruction revealed that the novel species SW510 can encode both cytochrome cd1-type nitrite reductase and hydroxylamine oxidase for nitrite reduction.In contrast,the detected respiratory pentaheme cytochrome c nitrite reductase and acetate kinase genes suggested that SW773 likely reduced nitrite to ammonium with acetate as a carbon source.Intriguingly,the presence of genes encoding urease and cyanase indicated that both novel species can use diverse organic nitrogen compounds in addition to ammonia and nitrite as substrates.Taken together,the recovery and comparative analysis of these anammox genomes expand our understanding of the functional differentiation and cooccurrence of the genus Ca.Brocadia in wastewater treatment systems.

Removal of airborne microorganisms emitted from a wastewater treatment oxidation ditch by adsorption on activated carbon

Bioaerosol emissions from wastewater and wastewater treatment processes are a significant subgroup of atmospheric aerosols. Most previous work has focused on the evaluation of their biological risks. In this study, however, the adsorption method was applied to reduce airborne microorganisms generated from a pilot scale wastewater treatment facility with oxidation ditch. Results showed adsorption on granule activated carbon （GAC） was an efficient method for the purification of airborne microorganisms. The GAC itself had a maximum adsorption capacity of 2217 CFU/g for airborne bacteria and 225 CFU/g for fungi with a flow rate of 1.50 m^3/hr. Over 85% of airborne bacteria and fungi emitted from the oxidation ditch were adsorbed within 80 hr of continuous operation mode. Most of them had a particle size of 0.65-4.7 μm. Those airborne microorganisms with small particle size were apt to be adsorbed. The SEM/EDAX, BET and Boehm＇s titration methods were applied to analyse the physicochemical characteristics of the GAC. Relationships between GAC surface characteristics and its adsorption performance demonstrated that porous structure, large surface area, and hydrophobicity rendered GAC an effective absorber of airborne microorganisms. Two regenerate methods, ultraviolet irradiation and high pressure vapor, were compared for the regeneration of used activated carbon. High pressure vapor was an effective technique as it totally destroyed the microorganisms adhered to the activated carbon. Microscopic observation was also carried out to investigate original and used adsorbents.